Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic disease of the lung unaffected by currently available medical therapies. Although traditionally considered a chronic progressive disease it has been recently recognized that patient's course may differ and that while some patients have a chronic slow decline in their pulmonary functions others have a more accelerated course characterized by "acute exacerbations". The variable course of the disease and the recent observation that improvement in patient survival does not have to be associated with an improvement in traditional pulmonary function tests, suggest that traditional methods for tracking IPF progression may at best serve as chroniclers of a forgone conclusion and not provide any useful information about disease progression. We hypothesize that host defense factors, potentially but not necessarily associated with the primary cause of the disease, determine the rate of disease progression. Characterizing these factors will allow us to identify an integrated set of surrogate biomarkers in the peripheral blood that correlate and potentially predate IPF progression. The proposal has the following specific aims: 1. To create, using the Simmons Center ILD Database and referral base, and the Short term IPF outcome study, a cohort of carefully characterized IPF patients that will be prospectively clinically followed up according to current clinical practice guidelines. 2. To analyze protein expression levels in the serum of target molecules using a multianalyte bead based protein profiling assays assay. 3. To identify a gene expression signature in PBMC that is diagnostic and relevant to disease progression and treatment effect. 4. To determine the role of adaptive immunity in IPF disease progression.